In a recording method by an ink jet printer, which is one typical method among a variety of color recording methods, recording is executed by generating ink droplets, which adhere onto any of a variety of record-receiving materials (e.g., paper, film, and fabric, etc.). According to this method, a recording head is not brought into direct contact with the record-receiving material; therefore, generation of noise can be reduced thus achieving silent recording. In addition, due to having the feature of reduced size and increased speed being readily achievable, prevalence in recent years has been in rapid progress. Accordingly, great advancement of the method hereafter is expected.
Aqueous inks prepared by dissolving a water-soluble dye in an aqueous medium have been used as conventional inks for fountain pens, felt pens etc., and inks for ink jet printing. Into these inks is generally added a water-soluble organic solvent in order to prevent pen tips or ink discharge nozzles from clogging with the ink. In addition, for these inks, demanded are ability to generate a recorded image with satisfactory density, probability of avoiding occurrence of clogging at the pen tips and nozzles, favorable drying characteristics on the record-receiving materials, suppression of bleeding, superior storage stability, and the like. Furthermore, water soluble dyes for use in the inks are required to have high solubility particularly in water, and high solubility in water soluble organic solvents added to the inks. Moreover, formed images are desired to have image fastness properties such as water resistance and light resistance, as well as color reproducibility.
Of these, in regard to the color reproducibility, an ink set including four dye inks each of a different color, i.e., black, yellow, magenta and cyan has been generally used. Thus, development of an ink set which is capable of providing recorded matters having high quality and high fastness properties, and is also superior in discharge stability has been demanded. To meet such demands, a variety of ink sets for ink jet recording have been proposed thus far; however, a broad hue range visible by human eyes cannot be completely reproduced by conventional ink sets, whereby a problem of narrow color reproducible range has existed.
In attempts to solve this problem, Patent Documents 1 to 8 propose an ink set for ink jet recording that is a combination of dye inks of yellow, magenta and cyan, each having perceived chromaticity indices “a” value and “b” value on a printing paper falling within a specific range. However, the inks disclosed in Patent Documents 1 to 8 are reportedly inferior in color reproducibility in a hue range of magenta-blue-cyan. Accordingly, an ink set containing a direct dye, an acidic dye, or a reactive dye as a coloring agent, and having sufficiently broad color reproducible range in this hue range has not yet been provided.
On the other hand, as magenta coloring agents suited for dye inks for ink jet recording, for example, C. I. Direct Red 227 disclosed in Patent Documents 1, 5 and 10, a compound represented by the formula (1), etc., have been known, and as cyan coloring agents, for example, C. I. Direct Blue 199 disclosed in Patent Documents 2 to 9, as well as C. I. Direct Blue 86 (a+b+c+d=2), 87 (a+b+c+d=3), C. I. Acid Blue 249 (a+b+c+d=4), etc., as compounds represented by the general formula (2) have been known.    Patent Document 1: Japanese Unexamined Patent Application, Publication No. H5-214259    Patent Document 2: Japanese Unexamined Patent Application, Publication No. H10-329403    Patent Document 3: Japanese Unexamined Patent Application, Publication No. H11-199815    Patent Document 4: Japanese Unexamined Patent Application, Publication No. 2000-109737    Patent Document 5: Japanese Unexamined Patent Application, Publication No. 2001-192591    Patent Document 6: Japanese Unexamined Patent Application, Publication No. 2003-128965    Patent Document 7: Japanese Unexamined Patent Application, Publication No. 2003-138169    Patent Document 8: Japanese Unexamined Patent Application, Publication No. 2003-238870    Patent Document 9: Japanese Unexamined Patent Application, Publication No. 2000-303009    Patent Document 10: Japanese Patent Publication No. 4497448